Dock bridge



Jan. 27, 1953 w. E. PALMER DOCK BRIDGE Filed April 25, 1949 IIIIII I II. I

Patented Jan. 27, 1953 UNITED STATES PATENT OFFICE 12 Claims.

This invention relates to an improved dock bridge-that is, an apparatus for bridging the gap between a loading dock and a freight car parked adjacent thereto.

The transfer of goods to or from a box car is nearly always accomplished when the car is placed adjacent a loading platform, commonly called a clock, which usually forms a part of the freight house, factory, or other point from which freight is being sent or to which it is being delivered. In general, the docks employed for freight loading are constructed at a height from the ground approximately equal to that of the floor level of a freight car.

Ideally, of course, the loading dock should be built so that its level is exactly that of the floor in the freight car and with its forward face at a position such that the car would clear it by only a very slight amount-perhaps an inch or less. Such construction would make it possible to run trucks back and forth between the car and the loading truck and thereby most readily transport goods to or from the car.

The ideal situation just described cannot be achieved in practice because there is no uniformity in the structure of freight cars. Box cars vary in width over a range of more than a foot. The floor heights vary over substantially an equal range. As a consequence, it is necessary that loading docks be designed to give clearance to the widest car, and the height must be chosen somewhere in the mid-range of variation of carfioor heights, in order to avoid an excessive difference in height between the car floor and the dock. Necessarily, therefore, a substantial gap, ranging from several inches to a foot, separates the box car from the loading dock in nearly all cases. In the past, this space has customarily been bridged by a steel plate or by a crude bridge formed of wooden planks. The arrangement has been ineflicient and dangerous, and has caused frequent personal injuries and damage to property. Control of such a bridge, to prevent it from slipping off the side of the car floor or dock, has posed a serious problem, especially in cases where considerable difference in height existed between the car floor and the dock. Often a rough solution has been to nail the bridge to the car fioor. This arrangement has not added materially to the safety of the dock bridge, but it has resulted in the destruction of many a car floor. In fact, it is well known in the railroad industry that box car floors must be replaced much more frequently than other parts of the car, largely due to the punishment given them in the attempt to safely attach crude dock bridges.

Another shortcoming of prior-art methods of bridging the gap between car and dock arises from the fact that no uniformity exists with respect to the width of car door openings. The planks or crude metal bridges in general use had to be made narrow enough to enter the narrowest door openings, with the. result that.

they failed to take full advantage of the space afiorded by the cars having wide door openings.

One of my objects in this invention is to provide an improved dock bridge, the operation of which does not involve physical risk to workers and which is adaptable to operate successfully with any car-floor height within a wide range. Another object of this invention is to provide a dock bridge for installation in a loading dock which will fully co-operate with the car door opening across its entire width and wherein the bridge may be securely and safely anchored to the car regardless of the width of the door open- A still further object of my invention is to provide a power-operated dock bridge which is counterweighted to place a minimum of strain on the power apparatus and to permit manual actuation when necessary.

Still another object of my invention is to provide a novel hook linkage for securing a dock bridge to the side of the car, comprising pivoted hooks which, when not in use, can be swung into a hanging position where they cannot interfere with passing cars.

Another object of my invention is to provide, in a hook linkage for securing a dock bridge to the side of a car, a novel telescoping brace which provides reinforcement for the grapple hooks and at the same time almost completely fills the residualgap between the forward edge of the dock bridge and the edge of the car floor.

Other objects and advantages of my invention will appear as the specification proceeds.

One form of my invention is illustrated in the accompanying drawing, of which Figure 1 is a fragmentary plan view, partly in section, of a loading dock and a portion of a box car, showing a dock bridge made according to my invention; Fig. 2, a sectional View of the structure of Fig. 1, the section being taken in the vertical plane along the line 22 of Fig. 1; Fig. 3, a fragmentary perspective view showing in detail the structure of my novel 'hook linkage for securing the dock bridge to the car; and Figs. 4 and 5, perspective views respectively of alternative parts which may be substituted for the hook member proper shown in Fig. 3.

In the drawing, l0 denotes a concrete loading clock. It will be understood that my invention may be applied'in connection with a dock of any construction and that concrete has been chosen only for purposes of illustration. Dock I0 is equipped with a recess ll having vertical side walls II a and aslanting bottom which curves gradually downward from the flat upper level of clock Ill. The bottom of recess I l is provided with a deeper and smaller recess [2, shown in Fig. 2, the function of which is to accommodate a counterweight member to be hereinafter described.

Securely set into corresponding positions in each of the side walls Ha of recess H is a pivot pin [3. Since pins 13, at certain stages of the operation of my dock bridge, may be subjected to considerable stress; itis-important that those pins be heavily constructed and firmly anchored in the side walls Ila.

The runway or tread member of my dock bridge is denoted I4 in the drawing and is normallymade. of strong sheet steel, capable of, withstanding the considerable weight of a heavily laden hand truck. For convenience in mounting and to insure amaximum of strength, I prefer that runway member I4 be equipped with side walls Ida, welded to or formed integrally with the flat top surface l4. A pairof transverse girders I4b connect the side walls I4'a'and reinforce the same; girders l'4balso provide a support for thecounterweight I5 which is rigidly aflixed to girders I 4b and received for the most part within recess I2. Weight I5 may be a concrete block or any other suitable weight sufficient in magnitude to place the center of gravity of member I4 at a point only slightly ahead of the mid-line'of runway member I4, considering the forward end. to be that nearest the edgeof dock I0;

At a point'in each of the side walls l4a slightly rearward of' the center of gravity an enlarged aperture IE is provided. Each of the apertures l6 fits over one of the pins It so that runway member I4 is confined to the rangeof movement perm tted by'the'fact that aperture I6 is substantially larger than pin l3. Each of the apertures I6 is provided with a. downwardly-proiecting dog orfinger I6'a located on its upper edge near its forward end; As will be" seen fromv the dotted outline ofanerturev I6 inFig: 2; the, movement: of run ay member; I4 backward: towardl retracted position causes dog-I611 to-ride up on and'over-pin I3, with the result that when runway member I4 is in completely retracted position, the pins I3 are lod ed securely in the upper, forward portion of apertures IS- and the runway member I 4 s held against chance forward movement by the dogs I 60; pressing a ainst pins I 3;

A plurality of rollers ll may be provided on the lower edges of sidewalls Ha to reduce frictional effects resulting from contact between side walls Ma and the bottom surface of recess II. The rearm'ost pairof rollers I 'I'will normally be in contact with the bottom of recess I I except when the run ay member I4 is in a particularly elevated pos tion. The more. forward rollers I! will usually beheld clear of the bottom of recess II except when the member I 1 is in retracted position.

Movement of member I 4a'from retracted to advanced position is accom lished by a power cvlinder- I8- containinga piston I9 to which is affixed a piston rod 2!]. Power cylinder I8 is supported on a' bracket 21 having a base'wh ch is securely anchored into the bottom of rece s II and a bifurcated upper portion 21a providing pivots for support of cylinder I 8. As may be seen from Fig. 2, cylinder I8; is free to swing on its pivoted mounting;

Piston rod 20' is pivoted to a; bracket 22 which isbolted or otherwise affixed to. the under side of runwaymember I.4..

Pneumatic conduits 23 connect: the respective endsof'cylincler I8 toa suitable. source of suction or compressed air and" suitable control apparatus (not shown). Since pneumatic actuating apparatus of the-type used in my invention is old and well-known, no detailed explanation or description thereof is believed necessary. In the present case, valve means are required which will, at the operators choice, provide a fluid pressure differential between the-respective: ends of cylinder I8 so as to accomplish movement of piston I8. While the task required can readily be accomplished by the use of vacuum, it will be assumed in discussing the operation of this embodiment of my invention that cylinder I8 is actuated by compressed air at super-atmospheric pressure.

Across the front of member I4, at slightly spaced distances below the flat top thereof, a pair of bars or rods, denoted 24 and 25 respectively, are mounted between the side walls [4a. A pair of brackets 26, welded or bolted to the flat under surface of member [4, serve to reinforce and strengthen the bars 24 and 25. This precaution is desirable since, as will beseen, a considerable stress is at certain times imposed on these. crossbars.

A pair of hook members 2'! are carried bycrossbar 24; as may be best seen in Fig. 3, the members 21 are provided with an elongated rear portion having width equal to the vertical distance between the upper surface of bar 25 and the under surface of member i4. This elongated rear portion is provided with a slot through which bar' 24 passes. Each of the members 21 is provided near its front end, a short distance anterior to bar 24, with a telescoping member; the largerv of thesaid members is denoted 28 and the smaller 29.

The extreme forward end of members 21 is provided with an extension 30 which serves as the hook means for securingv the dock bridge to the freight car with which it is being used. Member 39 has a hook portion 3011 designed to engage the sides of the door openingin a box car; member 30 is removably bolted to member 27 by bolts 3!.

As may be seen by reference-to Fig; 2, the members 21, when in use to support'member I4 and to secure it in a box-car entrance, occupy a position wherein the rear elongated extension is inserted between the under side of member I4 and bar 25, so that the stress imposed by the weight passing over member I4 is taken up partly by bar 24 and partly by bar 25. When the dock bridge is not being used, the hook members 21, by being pulled forward, are freed from engagement with bar 25' and can drop to the dotted-line position shown in Fig. 2. Thus when they are not in use members 21 are hangin down where they are out of the way and where there is no danger of their interfering with freight cars being shunted back and forth in front of the loading dock.

Figs. 4 and 5 show alternative members, 32 and 33 respectively, which may be substituted for member 30. Member 32 is similar to 30 except that it is substantially longer; it is primarily for use with refrigerator cars which have very thick walls which therefore require unusually elongated hook members on the dock bridge. Member 33 is a utility device adapted for use with the occasional car which, either by reason of damaged door jambs or unusual conformation, will not provide a secure seat for hook members 30 or 32. Member 34 has no hook projection on its forward end but is provided with a horizontal flange 33a which is equipped with apertures which can be used to nail member 33a, to a box-car floor.

Operation,

When my invention is not in use it will normally have been pulled, by appropriate actuation of power cylinder l8, into a completely retracted position. The dotted line showing in Fig. 2 illustrates the position of runway member I4 and its associated parts when they are approaching fully retracted position. When fully retracted, dogs iEa will ride over pins I3 and drop into position behind them, cylinder l8 will pivot into a position substantially vertical, and the forward edge of member 14 will assume a position only slightly in advance of the front edge of dock [0. Now assume that, as shown in Figs. 1 and 2, a box car 35 is brought into position adjacent dock In for loading or unloading. The doors 36 of car 35 will then be opened and swung back to expose fully the door opening of the box car. The operator will then slide members 21 toward one another along bar 24 until each of them is substantially inboard of the sides of the door opening in car 35. Each of the members 21 will then be shifted into its operating position, as shown in solid lines in Fig. 2, and power cylinder I8 should thereupon be actuated by supplying compressed air to the lower end of the cylinder.

In response to force of the compressed air, piston l9 will advance and runway member M will rise, at the same time moving forward because of the balance of weight ahead of pivot pins l3. As the runway member 54 approaches the floor of car 35 a member of the loading crew waiting in the box-car door can move members 2! outward until the hooks 30a are firmly in engagement with the sides of the door opening of car 35. In so moving members 22', the operator will also extend telescoping members 28 and 29. When the dock bridge has reached the position shown in Fig. 2, where the hooks 30a are in engagement with the sides of the door opening and the flat surface of member I4 is at the level of the floor of car 35, the pneumatic power can be shut off from cylinder i8 and both sides of the piston released to atmosphere, so as to permit member M to settle into position, the stresses thereof being divided primarily between hook members 21 pressing on the floor of car 35 and the rear edge of member 14 or the rear set of rollers ll pressing on the bottom of recess II. In very low positions there may be some of the stresses taken up by contact between apertures l6 and pivot pins l3, although this will not normally be the case.

In order to avoid the necessity for precise timed relationship between the setting of hook members 21 and the shutting off of power cylinder [8, a safety valve IBa may be provided in the lower end of cylinder [8, so that when the dock bridge has been placed into position the compressed air will, upon exceeding a critical pressure, escape through valve lBa rather than needlessly force the dock bridge against the side of the car and thus stall the piston l9.

As may be seen from Fig. 2, if the floor of the car being worked with is unusually low, the cylinder I8 may swing around on its pivots until it is in a substantially horizontal position.

The telescoping members 28 and 29 serve to close up almost completely the gap between the car floor and the dock bridge which would otherwise result from the presence of the doors 36 beyond the edge of the car floor. As a result, with the use of my dock bridge, a safe, stable means is afiorded for trucks and foot traffic back and forth between the car and the loading dock.

The counterweight I 5 is a highly desirable addition to my invention for the reason that it greatly lightens the burdens of the power cylinder [8 and also makes possible the operation of the dock bridge by hand in a situation where compressed air or vacuum is not available. It will be understood that the cylinder I8 should normally be left with both sides open to atmosphere 6 except when it is actually performing work, in order to permit manual movement of runway member l4 and its associated parts without the necessity for dragging piston l8.

When the loading or unloading of car 35 has been completed; the hook members 21 are released from the sides of the door opening. If necessary, member l4 may be lifted slightly by momentary application of air to cylinder l8 in order to facilitate such release. The members 21 are then slid toward one another sufficiently to enable them to slip between the door jambs readily and the cylinder It! will then be actuated in reverse, with high pressure applied to the upper end of the cylinder, to pull the dock bridge back into retracted position. As soon as the bridge has cleared the side of the car sufilciently the hook members 21 can be dropped to their hanging position, as shown in dotted lines in Fig. 2.

As may be understood from the foregoing description of the operation of my invention, my dock bridge will provide a safe, stable and strong passageway between a dock and freight car regardless, within wide limits, of the distance between the car and dock, the height of the car floor, or the width of the car door opening. Normally, the width of recess H and runway member M can be made substantially greater than the width of the car door opening, so that maximum safety, stability, and convenience are achieved. Similarly, by appropriate substitution of alternative hook members for hooks 33, my dock bridge can be adapted to cars having any wall thickness.

I have shown herein the alternative hook members 32 and 33 purely as an illustration of one possible means of adapting my structure to cars of greatly varying wall thickness. An alternative means which can accomplish a similar result consists in placing on crossbar 24 a plurality of pairs of members '21. With such an arrangement the centermost pair of members 21 need have no hook member 39 at all, their sole function being to support the telescoping members 28 and 29. Each pair of other members 2! may carry hook members of a particular length or conformation adapted to deal with a type of car frequently encountered. The use of such an arrangement in my invention would thus involve using the innermost members 21 for support of the telescoping members 28 and Z9 and whatever pair of other members 21 carry hooks appropriate to the particular car being dealt with. Those members 2'! not in use would hang down in the position shown in Fig. 2 and would in no way interfere with the operation.

While I have in this specification described in considerable detail one embodiment of my invention, such description was for exemplary purposes only. It will be understood that many variations in detail can be made without departing from the spirit of my invention; accordingly I desire that the scope of my invention be determined solely by reference to the appended claims.

I claim:

1. Grappling mechanism on a movable dock bridge comprising a transverse bar secured to the bridge and a pair of hooks slidably mounted thereon, said hooks being pivoted to permit their being dropped to hang from the bar when not in use, said hooks being also joined by a telescoping member extending transversely of the bridge across the space between the hooks to fill a portion of the gap between the bridge and the car when the hooks are securing the bridge to a car-door opening,

2. Apparatus according to claim 1 wherein the hooks are formed in two detachable pieces, one of which is permanently pivoted to the transverse bar and the other is one of a plurality of alternative members adapted to fit car doors of substantially differing thicknesses.

3. Grappling mechanism on a movable dock bridge comprising a transverse bar secured to the bridge and a plurality of members slidably carried thereon, said members being pivoted to permit their being dropped to hang from the bar when not in use, the innermost pair of said members being joined by a telescoping member extending transversely of the bridge across the space between the hooks to fill a portion of the gap between the bridge and the car when the bridge is in operating position, the remainder of said members being formed in pairs, the respective pairs being provided with hooks adapted to co-operate with car walls of varying thicknesses.

4. A Cook bridge mounted in a recess in a loading dock, comprising a runway member, retaining guide means securing the runway member within the dock recess while afiording said member a limited range of movement relative to said dock, power means mounted in the dock recess, means pivotally coupling the power means to the runway member operative on actuation of the power means to move the runway member upward and outward from the dock, and a pair of slidably mounted hook members carried by the runway member and provided at their forward ends with hooks adapted to engage the sides of the car door opening, each of said hook members carrying also a transverse member telescoping with the corresponding transverse member of the other hooks, such telescoping members being operative to reduce the gap between the car and the runway member when the hook members are secured to the car.

5. In a dock bridge mounted in a recess provided by a loading dock, a runway member pivotally supported at its inner end in said recess and also supported for in and out movement with respect to said dock, a rigidly-mounted pin extending transversely across said recess, said runway member being equipped with depending side walls each providing an enlarged U-shaped aperture aligned with and receiving said pin, and outwardly-inclined piston means mounted in said recess and secured to said runway and being operative to efiect upward and outward movement of said runway.

6. The structure of claim 5 wherein said recess is equipped with spaced-apart facing side walls and said pin is carried by the side walls.

7. The structure of claim 5 wherein the upper edge of each U-shaped aperture is equipped with a depending dog that rides over said pin upon in and out movement of said runway member.

8. In a dock bridge mounted in a loading dock recess having a downwardlyand outwardlyinclined bottom wall, a runway member equipped with spaced-apart depending side walls, a rigidlymounted transverse pin extending across said dock recess, said depending side walls each providing an enlarged U-shaped aperture aligned with said transverse pin and receiving the same, a roller carried by said depending side walls adjacent the inner end of said runway and resting upon said bottom wall to provide a support for said runway, said runway being vertically pivotal about saidroller and movable in and out thereon with respect to said recess and within the limits provided by said pin and U-shaped apertures, and outwardlyand upwardly-inclined piston means mounted insaid recess and secured to said runway and being operative to effect upward and outward movement of said runway.

9. The structure of claim 8 in which the upper edge of each of said apertures is equipped with a depending dog over which said tranverse pin rides upon in and out movement of said runway member, and said runway member is equipped with a counterweight adjacent its inner end.

10. A dock bridge mounted in a recess in a loading dock, comprising a runway member, retaining guide means securing the runway member within the dock recess while affording said member a limited range of movement relative to said dock and including a pin mounted in said recess and extending into an enlarged opening provided by said runway member, outwardlyinclined power means mounted in the dock recess, means pivotally coupling the power means to the runway member operative on actuation of the power means to move the runway member upwardly and outwardly from the dock, and hook means carried by the runway member for engaging the door opening of a car parked adjacent the dock.

11. A dock bridge mounted in a recess in a loading dock, comprising a runway member, retaining guide means securing the runway member within the dock recess while affording said member a limited range of outward and upward movement relative to said dock and including a pin, mounted in said recess and extending into an enlarged opening provided by said runway member, power means mounted in the dock recess means pivotally coupling the power means to the runway member operative on actuation of the power means to move the runway member upwardly and outwardly from the dock, and a pair of hook members carried by the runway member and each being transversely slidable with respect thereto so that the separation of the hook members is adjustable to correspond to the width of the door opening of the car, said hook members being provided at their forward ends with hooks adapted to engage the sides of the car door opening.

12. The structure of claim 11 in which a transverse bar is mounted on the runway member along the front edge thereof, and said hook members are slidably mounted upon said transverse bar, said hook members also being pivotally carried upon said transverse bar to turn thereon and hang downwardly and out of the way when not in use.

WILLIAM E. PALMER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 502,568 Kuckartz Aug. 1, 1893 813,046 Janssens Feb. 20, 1906 1,358,951 Helmich Nov. 16, 1920 1,905,947 Morgan Apr. 25, 1933 2,449,829 Agren Sept. 21, 1948 2,491,870 McLaughlin Dec. 20, 1949 OTHER REFERENCES Architectural Record-October, 1948, page 179. 

